The pursuit of increasing quality, productivity, and product yield within the semiconductor manufacturing industry is an ongoing endeavor. To that end, the industry has developed techniques to improve operative yield by “trimming” or electrically removing inoperable or defective memory or other circuits from the main circuit. In such instances, the integrated circuit also includes redundant memory arrays or circuits that are laid out so that they can be electrically incorporated into the integrated circuit design when the defective portions are detected. In the event that a given memory block is defective, that block can be effectively “trimmed” or electrically removed from the circuit by use of a fuse or a group of fuses that electrically disconnect the defective component from the main circuit. When a defective memory block or circuit is detected, the relevant fuse or fuses are “blown” to an open configuration such that the defective memory block or circuit is electrically removed from the circuit.
One way in which this objective has been achieved is by the use of a poly semiconductor e-fuse. A conventional poly semiconductor e-fuse typically consists of a polysilicon body that has a very narrow neck region and that is doped with a single type of dopant. The dopant used in such conventional devices is an N-type dopant, such as arsenic or phosphorous, and in many cases both are used, and is necessary to obtain good metal silicidation on the poly e-fuse. The polysilicon e-fuse is positioned within the circuit such that when it is opened or blown, it disconnects the defective component from the main circuit. A logic algorithm is then used to direct the data stream to the redundant memory block or circuit. The fuse is blown by applying a relatively high voltage to the polysilicon e-fuse such that the conductive layer in the narrow neck region melts. In most some instances, the underlying body portion of the polysilicon e-fuse also blows such that the two portions of the polysilicon e-fuse are completely and physically separated from each other.
However, in some instances, the body portion of the fuse does not physically separate, or if the fuse is successfully blown, the polysilicon can migrate, due to thermal and physical stresses, to re-establish a conductive path across the fuse. This can cause problems because in either instance the polysilicon e-fuse is still conductive, which causes the trimming effort to fail.
To circumvent the problems associated with these poly e-fuses, the industry has turned to the use of contact fuses. A contact fuse employs the use of a wide polysilicon body that does not include a narrow neck region as does the poly e-fuses. Further, they are different in that instead of blowing a region of the polysilicon, a contact that contacts the polysilicon is blown. While, the yield of contact fuses is very high and much better than the earlier polysilicon e-fuses, they too have disadvantages. In a small percentage of these fuses, the contact will sometimes blow near the top of the fuse, which is typically connected to a copper interconnect. In such instances, the blow will free copper that can then migrate to dielectric materials and the poly fuse body and create a conductive path to an adjoining structure under operational electrical bias. The free copper significantly degrades the device reliability. This allows an electrical connection to remain in place and decreases the fuse reliability within the device.
Accordingly, what is needed is a semiconductor device that avoids the disadvantages associated with the current devices.